1. Field of the Invention:
This invention relates to a system for treating wastewater.
2. State of the Art:
Domestic sewage and industrial wastewater often contain impurities which include materials such as sugars and other carbohydrates and proteins and other forms of nitrogen. Many of these impurities or pollutants are decomposable by microorganisms, and there are various types of systems to remove the impurities from wastewater by action of microorganisms. One type of wastewater treatment system is known as an orbital system, sometimes referred to as an oxidation ditch system.
Generally speaking, an orbital wastewater treatment system includes an elongated tank having two sidewalls and at least one partition wall mounted vertically in the tank substantially parallel to the two sidewalls and spaced apart from the ends of the tank. The tank and partition wall together form an endless, circuitous channel to contain a stream of liquid. An orbital wastewater treatment system also includes means to cause the liquid to flow through the channel and an aerating means to introduce air into the liquid to provide oxygen for the microorganisms. Orbital wastewater treatment systems are taught, for example, in U.S. Pat. Nos. 3,510,110 and 3,846,292. According to U.S. Pat. No. 3,846,292 influent wastewater is introduced into the tank and driven to flow around the endless, circuitous channel. A stream of treated liquid, less than the total flow in the channel, is removed from the channel and transferred into a solid-liquid separator, or clarifier, spaced apart from the orbital system. In the separator, solid particles form sludge which settles, and part is returned to the orbital system to mix with the wastewater to form mixed liquor. Clarified liquid is transferred from the separator to a stream or other body of water. The purpose of returning sludge to the orbital system is to maintain a predetermined concentration of microorganisms in the mixed liquor thereby to accomplish biological removal of pollutants from the wastewater.
The construction of a conventional orbital system such as taught in the patent requires that the circuitous channel be constructed and that a separate sludge separation system also be constructed. Additionally, a system of pipes and pumps must be installed to permit diversion of wastwater from the orbital system to the separator and return of sludge from the separator to the orbital system.